>Thanks George, but it became clear after reading Steve's solution that my goal was wrong to begin with. Don't know what I was thinking. I need to switch the pairs not reverse them! Now I really know its Friday!

You mean you just want to switch pairs? A little adjustment then

lcstring = "RGB(0, 0, 0, 255, 255, 255)"
oRE = CREATEOBJECT("VBScript.RegExp")
oRE.Pattern = "(\d+)\, (\d+)\, (\d+)\, (\d+)\, (\d+)\, (\d+)"
? oRE.Replace(lcstring, "$2, $1, $4, $3, $6, $5")